1. Field of the Invention
The invention relates to unstacker apparatus for unstacking flat items, the unstacker apparatus comprising a flat item feed magazine in which the flat items are disposed in a stack and on edge and are moved in a certain direction until they reach an unstacking plate disposed in alignment with said feed magazine, whereupon they are ejected one-by-one in a perpendicular direction that is perpendicular to said certain direction, the unstacker apparatus further comprising a blower member disposed so as to blow a jet of air onto the flat items.
The invention relates more particularly to unstacker apparatus for unstacking postal items of small format and of large format in a postal sorting machine. The blower member contributes to fanning out the postal items at the front of the stack against the unstacking plate, and makes it possible to limit occurrences of bunches of postal items that fail to separate.
2. Discussion of the Background Art
Patent Document FR 2 797 856 discloses apparatus for unstacking postal items that is designed to be mounted on a postal sorting machine. That apparatus 1, described below with reference to FIG. 1, is provided with a motor-driven magazine M having a substantially horizontal surface and comprising, in particular, a conveyor belt 2 on which an operator disposes postal items E on edge that are to be put into series, and a substantially vertical paddle 3 that is also motor-driven, that is mounted to move along a rail 4, and that is designed to push the stack in a certain longitudinal direction indicated by arrow D towards an unstacking plate 6. The postal items in the stack are aligned and held laterally by a jogger edge 5 extending vertically in said longitudinal direction along one edge of the magazine M. The unstacking plate 6 extends vertically and each first postal item in the stack having its large face bearing against the unstacking plate is ejected in a direction P that is perpendicular to the direction D towards the outlet of the unstacker.
The unstacking plate 6 is provided with an opening in the plane of which a perforated belt 8 is moved, which perforated belt co-operates with a suction nozzle (not shown) mounted behind the perforated belt. In operation, the stack of postal items E is moved by the conveyor belt 2 and by the paddle 3 towards the unstacking plate 6, and the first postal item in the stack comes to bear against the unstacking plate 6. That postal item in the stack, i.e. the postal item that has its large face pressed against the unstacking plate and that is referred to as the “current first postal item” E1, is ejected in the direction P under the combined effect of the suction force from the nozzle and of the movement of the perforated belt 9. That postal item is nipped between motor-driven wheels 9, 10 having vertical axes and made of elastically deformable elastomer so that it is ejected at the outlet of the unstacker apparatus that is situated in the plane of the plate 6.
All of the postal items in the stack are thus successively put into series one behind another in the same way, i.e. the postal item E2 disposed in the stack immediately behind the current first postal item E1, is ejected at the outlet of the unstacker immediately after the postal item E1.
In general, the postal items unstacked one-by-one are conveyed in series and on edge so as to be brought past a read head. An image of the face bearing the destination address of each postal item is extracted by the read head and is processed in an automatic address recognition system by Optical Character Recognition (OCR) so that the postal items are directed to specific sorting outlets.
With the unstacker apparatus of the Patent Document FR 2 797 856, a non-negligible proportion of postal items are observed to be taken in bunches. The term “bunch” is used to mean that a plurality of (generally two) postal items have been ejected simultaneously by the unstacker apparatus. Such postal item bunching give rise to sorting errors that are detrimental to the reliability of the sorting or to the throughput of the sorting machine because detection of such postal items results in them being rejected to a rejects sorting outlet followed by them being sorted manually.
Patent Document EP 0 562 954 discloses a solution to that bunching problem. That solution, presented in FIG. 2, consists in blowing a jet of air 11 onto the first few postal items in the stack of postal items E, i.e. onto the postal items that are close to the unstacking palate 6, e.g. between the first postal item E1 and the second postal item E2. The jet of air 11 is propelled by means of a blower member or strip 12. The jet of air 11 makes it possible to fan out the first few postal items in the stack relative to one another so that when the first item E1 is driven by the perforated belt 8, the second postal item E2, dissociated from the postal item E1, is not entrained by the postal item E1. The blower strip 12 is disposed at a height such that it overlies all formats of postal item that are accepted by the machine, including the largest format of postal items.
In unstacker apparatus suitable for unstacking both large-format postal items and small-format postal items, the blower strip thus finds itself very high up from the top edges of small-format postal items, and the effectiveness of the jet of air 11 in fanning out small-format postal items properly is therefore diminished. Unfortunately, bunching mainly affects small-format postal items.